Film perforating apparatus

ABSTRACT

The perforating apparatus disclosed includes a perforating roll which has a plurality of apertures in the shape of the perforations to be made in the film. Heated needles are positioned in each of the apertures and the surface surrounding the apertures is cooled below the melting point of the film. A pair of supplementary rolls position the film over the perforating roll so that the film is wrapped almost a full 360* as it is passed over the roll in the perforating process.

United States Patent Huppenthal et al.

1 Dec. 26, 1972 [54] FILM PERFORATING APPARATUS [72] Inventors: GeorgeAlfred Huppenthal, Neenah,

Wis.; Shlomo Peeri, Holon, Israel [73] Assignee: American Can Company,New

York,N.Y.

[22] Filed: July 21, 1970 [21] Appl. N0.: 56,837

v [52] U.S. Cl. ..83/171, 264/154, 83/170 [51] Int. Cl. ..B26f 3/08 [58]Field of Search ..83/16, 170, 171, 660; 264/D1G. 70, 154; 18/19 P, 19 R[56] References Cited UNITED STATES PATENTS 12/1967 Carmichael ..83/1713/1966 Hannaver, Jr. et a1. ..83/16 X FOREIGN PATENTS OR APPLICATIONS553,342 12/1956 Italy ..264/154 Primary Examiner-James M. MeisterAttorney-Robert P. Auber, George P. Ziehmer, Leonard R. Kohan, Ronald A.Schapira and Harries A. Mumma, Jr.

[57] ABSTRACT The perforating apparatus disclosed includes a perforatingroll which has a plurality of apertures in the shape of the perforationsto be made in the film. Heated needles are positioned in each of theapertures and the surface surrounding the apertures is cooled below themelting point of the film. A pair of supplementary rolls position thefilm over the perforating roll so that the film is wrapped almost a full360 as it is passed over the roll in the perforating process.

8 Claims, 2 Drawing Figures PATENTEI] DEC 26 m2 SHEET 1 BF 2 INVENTORS DWPPENTHAL I 1 1 GEORGE AL SHLOMO P FRE EER ATTORNEY PATENTEDnms 1912SHEET 2 0F 2 NQEM QM i w ww sw NW mm mm cw INVENTORS GEORGE 550HUPPENTHAL I ALF SHLOMBOY PE ATTORNEY FILM PERFORATING APPARATUSBACKGROUND OF THE INVENTION The present invention relates to apparatusfor perforating plastic film by means of heated needles.

Polyethylene and other plastic films have been widely used to packagefood for complete visual display on grocery counters. Often it isnecessary to perforate the film used in packaging to allow air to enterand to control the moisture content in the package so that the food doesnot become stale or rotten prematurely.

One common method for perforating plastic film involves the use of asimple mechanical punch. Generally, this method has been found deficientbecause the punched holes easily develop tears that reduce thedurability and strength of the completed package. In addition, thepunched out portions occasionally remain attached to the edges of theperforations. This residue subsequently may be detached and become mixedwith the packaged food.

Another general method, which is the subject of the present invention,uses heated needles to burn or melt a hole in the film. The perforationsmade by the needles have reinforced edges in the form of grommets thatresult from the melting of the film as the hot needles form the holes.As a result, the film is not easily torn in the area of theperforations. Another advantage is that, since the hole is burned ormelted through the film, there is no punched residue similar to thatwhich results in a mechanical punching operation.

The major problems associated with the use of heated needles are that itis difficult to regulate the size and shape of the resulting holes, andthat the perforating apparatus must generally run relatively slowly sothat the heated needles will have sufficient time to burn or melt thedesired hole in the film.

Accordingly, it is the object of the present invention to provide a filmperforating apparatus using heated needles that is capable of generatingholes of a con-.

trolled size and shape and is capable of operation at relatively highspeeds.

SUMMARY OF THE INVENTION The perforating apparatus of the presentinvention includes a perforating roll which has a plurality of aperturesin the shape of the perforations to be made in the plastic film.Needles, positioned in each of the apertures, are heated by means of anelectric current. The surface of the roll surrounding the apertures iscooled by water or other coolant circulating in the wall of the roll. Inaccordance with the invention the heated needles may either projectthrough the surface of the roll or remain below the surface within eachof the apertures.

In operation, the film is passed over the surface of the roll and isperforated by the heated needles. A pair of supplementary rolls withsmaller diameters than the perforating roll are positioned to hold thefilm in place around the perforating roll. The two supplementary rollsinsure that the film is wrapped around the perforating roll a maximumamount, almost a full 360. as the film is fed over the perforating roll.The heat from the needles in the perforating roll melts the film andcauses a bead-like grommet to be formed around the hole for resistanceto tearing. Since the cooled surface of the roll solidifies the meltingfilm surrounding the needles, the shape of the perforations is closelyregulated by the shape of the apertures in the roll. In addition, thesize of the perforations is determined by the positioning of the heatedneedles relative to the surface of the roll. In a preferred embodiment,the needles have a conically shaped nose that projects above the surfaceof the roll. The cross-sectional diameter of the nose at the surface ofthe roll increases as the nose projects further above the surface sothat the size of the perforation is affected by the relative positioningof the needles with respect to the surface.

In the past, the use of heated needles to perforate plastic films hasbeen limited by the slow speed-of the perforating apparatus. This slowspeed, in part, results from the fact that these prior devices useseparate rolls to carry the needles and to support the film to beperforated. Since the roll with the needles rotates about a differentaxis from the axis of the roll supporting the film, the length of thearc reflecting the path of continued contact between the needles and thefilm is limited generally to angles of less than A short are of contactindicates that the film is in contact with each needle a relativelyshort time in each cycle of the rolls. Since the needles must be incontact with the film for a predetermined minimum time to form properperforations, a limited arc of contact limits the speed of rotation ofthe rolls and thereby limits the speed of the entire perforatingprocess.

The advantage of the present perforating apparatus is that the film ispassed over a single perforating roll which has the heated needlesintegrated in well defined apertures. Since the heated needles cover theentire 360 surface of the perforating roll and since the film is passeddirectly over the roll, the film may be positioned for maximum contactwith the needles as the film is passed through the perforating process.As a result of the great arc of contact between the film and the heatedneedles, the film remains in contact with the needles for a relativelylong period and may be passed over the perforating roll at relativelyhigh speeds without affecting the uniformity of the hole size. Inaddition, the chilled surface closely surrounding the heated needlespermits close regulation of the size and shape of the holes and grommetsas the film is passed over the roll. A

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of thefilm perforating apparatus of the present invention, and

FIG. 2 is a partial sectional view taken along the line 2-2 of FIG. 1.

DETAILED DESCRIPTION The perforating apparatus shown in FIG. 1 includesa perforating roll 10, film supply roll 11 and a perforated film take uproll 12. Two supplementary rolls 13 and 14 are positioned adjacent toone another and adjacent to the perforating roll 10. In the illustrativeembodiment shown in FIG. I the film 15 to be perforated is positionedunder the supplementary roll 14 and then continues to the take up roll12. The film 15 may be any of a number of plastic films, including suchfilms as polyethylene, polypropylene and Nylon Maraflex.

The purpose of supplementary rolls 13 and 14 is to wrap the film 15about the perforating roll 10 so that a contact surface of almost 360 isprovided with roll before the film is passed to take up roll 12. Rolls10, 1 l and 12 rotate about fixed axes. In addition, to insure propertightening of film about roll 10, supplementary roll 14 is preferably aconventional dancer roll suitably arranged to control a magnetic orsimilar braking device operating on supply roll 11, whereby the tensionof the web is properly controlled.

As shown for purposes of illustration, when .the perforating roll 10rotates in a counterclockwise direction, the film supply roll 11 alsorotates in a counterclockwise direction and the supplementary roll 13rotates in a clockwise direction. The film l5 continues around the roll10 and causes the supplementary roll 14 to rotate in a clockwisedirection. The take up roll 12 rotates in a clockwise direction torewind the perforated film after it leaves the supplementary roll 14.Perforating roll 10 and take up roll 12'may be powered by any of anumber of conventional means. Roll 12 may be axially oscillated slightlyto prevent any irregularities from developing in the roll of film as itis wound up on the take up roll 12, thus avoiding lumpiness of the filmroll due to the greater thickness of the grommet areas.

As shown in FIG. 2, the perforating roll 10 has a series of apertures inwhich are positioned heated needles 21. Each of the needles 21 containsa heating element 22 embedded in a conically shaped nose. An electriccurrent passing through wire pairs 23 and 24 heats the elements 22 sothat the needles will form perforations in the film 15. The apertures 20and needles 21 may be arranged in any desired format in the roll 10. Forillustrative purposes, the apertures and needles in FIG. 1 arepositioned uniformly throughout the cylindrical surface of the roll 10to form evenly spaced columns and rows of perforations in the film 15.

Perforating roll 10 is divided into an innerlayer 28 of insulatingmaterial and a surface layer 29 which cools the surface of the rollsurrounding the apertures 20. The surface layer 29 is chilled by meansof a coolant that flows through passages 25 formed in the layer 29, asshown in the sectional view of FIG. 2. The insulating effect of theinner layer 28 isolates the layer 29 from the heat of needles 2 1 andincreases the effectiveness of the coolant in passages 25. In thepreferred embodiment, the needles 2] are mounted on to the inner layerand do not contact the surface layer 29 so that a minimum amount of heatis transferred from the needles 21 to the chilled surface layer 29. Theinner layer 28 may be any of a number of conventional insulatingmaterials such as Transite or Marinite. In contrast, the outer layer 29is a heat conducting material which maintains the chilled surfaceprovided by the coolant in passages 25.

Electric current may be supplied to each of the wire pairs 23 and 24 inthe roll 10 from an external power source by any of a variety ofconventional methods. One method is to connect the powering apparatus tothe roll 10 by means of conventional electrical brushes (not shown) suchas are used in generators and electric motors so that the heatingelements 22 may be powered by the external source while the roll 10 isrotating. Each of the wire pairs 23 and 24 may be connected individuallyto the brushes, or the roll 10 may be supplied with an inner conductingring (not shown) connected between the brushes and the wire pairs 23 and24.

In FIG. 2 the nose of each of the needles 21 projects slightly above thelevel of the surface of roll 10. The needles may be mounted in the roll10 at fixed levels, such as at the level shown in FIG. 2, or they may bemounted adjustably in order to permit easy variation in the height ofthe needles relative to the surface of the roll. One simple means foradjustably mounting the needles is to thread the base of the needle,such as shown by 21 (a). In such a case, an adjusting and locking nut 30is mounted rotatably on the inside of the roll so that rotation of thenut adjusts the level of the needle.

At a constant speed of rotation of the perforating roll 7 and at aconstant temperature of the needles, the

amount of the projection of the nose of each needle 21 above the surfaceof roll 10 controls the size of the perforations made by the roll 10.If, for example, the nose of the needles 21 in FIG. 2 is raised relativeto the level of the surface of the roll 10, the resulting cross-sectional diameter of the needle 21 that intersects with the film 15 at thesurface of the roll is increased so that a larger hole is melted in thefilm. Correspondingly, if the needle 21 is moved lower with respect tothe surface of the roll 10, a smaller hole is produced in the film 15.

It should be noted, however, that the general shape of the resultingperforation is determined by the shape of the aperture. It should bealso noted that if the nose of the needle 21 remains below the surfaceof the roll 10, so that there is no initial contact of the needle 21with the film 15, the heat radiated by the nose still causes the film 15to melt, thereby forming a small perforation in the shape determined bythe shapeof the aperture in the surface of the roll 10.

Any smoke that results from the melting or burning of the film 15 as itpasses over the perforating roll 10 may be removed by conventionalexhaust removal'apparatus. When it is desirable to eliminate anypossibility of burning of the film 15, the entire perforating apparatusmay be enclosed in an inert atmosphere, such as nitrogen.

In conclusion, therefore, it may be seen that the above-describedperforating apparatus provides an economical-and flexible system thatmay be used for perforating a variety of types of plastic films. The

general shape of the perforations may be controlled by controlling theshape of the apertures in the perforating roll. Variations in thethickness of the film may be accounted for by adjusting the height ofthe needle nose relative to the surface of the roll 10. The generalshape of the perforations may also be varied byproviding means forvarying the size of the apertures as by the use of threaded femaleapertures in the roll and interchangeable threaded male apertureinserts. The apparatus may, in addition, be run at a maximum rate ofspeed because of the large arc of contact of the needles with the filmas it is passed over the perforating roll. It may be readily appreciatedthat the film 15 has a maximum contact with the roll 10 and the needles21 so that the needles remain in-contact with the film for a maximumamount of time. Thus, the above-described system provides for reinforcedperforations which are resistent to tearing and which may be producedeconomically at rapid rates of speed.

What is claimed is:

1. Apparatus for perforating a plastic film comprising:

a perforating roll supported for rotation, the outer surface of saidroll having a plurality of apertures;

a plurality of needles mounted to said roll and positioned in saidapertures;

means for heating said needles;

means for cooling the surface of said roll around said apertures;

means for feeding said film to said roll;

means for removing said film from said roll; and

means for positioning said film around the surface of said roll so thatsaid heated needles form perforations in said film as said roll isrotated.

2. Apparatus in accordance with claim 1 wherein said means forpositioning said film includes first and second supplementary rollerspositioned adjacent each other and adjacent said perforating roll sothat said film makes contact with a majority of the surface area of saidperforating roll.

3. Apparatus in accordance with claim 1 wherein each of said needles hasa conically shaped nose projecting above the surface of said rollthrough said apertures.

4. Apparatus in accordance with claim 1 wherein said needles arepositioned adjustably in said apertures.

5. Apparatus in accordance with claim 4 wherein said perforating roll isprovided with means for varying the area of each of said apertures.

6. Apparatus for perforating a plastic film comprismg:

a perforating roll rotating about a fixed axis, the

outer surface of said roll having a plurality of apertures of apredetermined shape;

a plurality of needles mounted to said roll and positioned in saidapertures, the cross-sectional size and shape of said needle at thesurface of said roll closely matching the size and shape of saidapertures;

means for heating said needles;

coolant passages in said roll and close to said surface,

through which passages a coolant flows;

recirculating means for continually supplying the coolant to saidpassages to chill the surface of said roll;

means for feeding said film to said roll;

means for removing said film from said roll; and

means adjacent said roll for tensioning said film around said surface ofsaid roll such that the majority of said surface area is contacted bysaid film as said roll is rotated.

7. Apparatus in accordance with claim 5 wherein said means forpositioning saidfilm around said roll includes first arid secondsupplementary rollers positioned adjacent each other, said film passingaround said perforating roll and between said rollers.

8. Apparatus in accordance with claim 5 wherein said perforating rollhas a heat conducting surface layer surrounding said passages and a heatinsulating inner layer to insulate said surface layer from the heat ofsaid needles inside said roll.

1. Apparatus for perforating a plastic film comprising: a perforatingroll supported for rotation, the outer surface of said roll having aplurality of apertures; a plurality of needles mounted to said roll andpositioned in said apertures; means for heating said needles; means forcooling the surface of said roll around said apertures; means forfeeding said film to said roll; means for removing said film from saidroll; and means for positioning said film around the surface of saidroll so that said heated needles form perforations in said film as saidroll is rotated.
 2. Apparatus in accordance with claim 1 wherein saidmeans for positioning said film includes first and second supplementaryrollers positioned adjacent each other and adjacent said perforatingroll so that said film makes contact with a majority of the surface areaof said perforating roll.
 3. Apparatus in accordance with claim 1wherein each of said needles has a conically shaped nose projectingabove the surface of said roll through said apertures.
 4. Apparatus inaccordance with claim 1 wherein said needles are positioned adjustablyin said apertures.
 5. Apparatus in accordance with claim 4 wherein saidperforating roll is provided with means for varying the area of each ofsaid apertures.
 6. Apparatus for perforating a plastic film comprising:a perforating roll rotating about a fixed axis, the outer surfacE ofsaid roll having a plurality of apertures of a predetermined shape; aplurality of needles mounted to said roll and positioned in saidapertures, the cross-sectional size and shape of said needle at thesurface of said roll closely matching the size and shape of saidapertures; means for heating said needles; coolant passages in said rolland close to said surface, through which passages a coolant flows;recirculating means for continually supplying the coolant to saidpassages to chill the surface of said roll; means for feeding said filmto said roll; means for removing said film from said roll; and meansadjacent said roll for tensioning said film around said surface of saidroll such that the majority of said surface area is contacted by saidfilm as said roll is rotated.
 7. Apparatus in accordance with claim 5wherein said means for positioning said film around said roll includesfirst and second supplementary rollers positioned adjacent each other,said film passing around said perforating roll and between said rollers.8. Apparatus in accordance with claim 5 wherein said perforating rollhas a heat conducting surface layer surrounding said passages and a heatinsulating inner layer to insulate said surface layer from the heat ofsaid needles inside said roll.